Developing Agents

Because agents have components in Python, C++, and UE5, creating agents is a rather involved process. This guide will walk you through each step of creating a new agent for BiguaSim.

General Agents

General agents do not have buoyant properties. They are the simplest agents to create. We will walk you through the process of creating a new agent by copying and modifying the TurtleAgent.

C++

In biguasim/engine/Source/HoloDeck/Agents, you will need to create four new files for your agent. Duplicate the following four TurtleAgent files listed below, and rename them accordingly:

  • TurtleAgent.cpp -> CustomAgent.cpp

  • TurtleAgent.h -> CustomAgent.h

  • TurtleAgentController.cpp -> CustomAgentController.cpp

  • TurtleAgentController.h -> CustomAgentController.h

Make sure the .cpp files are created in the Private folder, and .h files are made in the public folder.

In CustomAgent.h, do the following:

  • Change #include "TurtleAgent.generated.h" to #include "CustomAgent.generated.h"

  • Change class HOLODECK_API ATurtleAgent : public AHolodeckAgent to class HOLODECK_API ACustomAgent : public AHolodeckAgent

  • Change ATurtleAgent(); to ACustomAgent();

  • In the line, unsigned int GetRawActionSizeInBytes() const override { return 2 * sizeof(float); };, change the number 2 to however many inputs your agent has

  • In the line float CommandArray[2]; change the 2 to however many inputs your agent has

CustomAgent.cpp is where the bulk of an agent’s behavior is defined, including custom dynamics, reactions to inputs, and so on. Change the following for CustomAgent.cpp:

  • Change #include "TurtleAgent.h" to #include "CustomAgent.h"

  • Change all instances of ATurtleAgent to ACustomAgent

  • Add code for anything you want your agent to do and how it responds to inputs in the Tick(float DeltaSeconds) function

In CustomAgentController.h, do the following:

  • Change #include "TurtleAgent.h" to #include "CustomAgent.h"

  • Change #include "TurtleAgentController.generated.h" to #include "CustomAgentController.generated.h"

  • Change all instances of ATurtleAgentController to ACustomAgentController

In CustomAgentController.cpp, do the following:

  • Change #include "TurtleAgentController.h" to #include "CustomAgentController.h"

  • Change all instances of ATurtleAgentController to ACustomAgentController

Compile the C++ code using Visual Studio or the Unreal Editor. To do this with UE, open the holodeck.uproject file in Unreal Editor and click the compile button at the bottom right of the screen. Fix any errors until the code compiles successfully.

Unreal Engine

Navigate to Content/HolodeckContent/Agents in the content browser. Create a new folder for your agent, and go into it. You will need a static mesh and a blueprint for your agent.

For your agent static mesh, do the following:

  • Import your mesh into your new folder

  • Edit the mesh to add a socket named “Viewport” so that the camera can spawn correctly. If you wish to use other sensors, add other sockets for the location of those sensors.

../../_images/viewport-socket.png

For your agent blueprint, do the following:

  • Right click and select to create a blueprint class. You will get a dialog asking you to choose your parent class. Choose your C++ class (CustomAgent) from the previous step, and name your new blueprint something like CustomAgentBp

  • Insert any custom meshes for your agent. For help with this step, find tutorials online for making custom pawns in UE

  • Make sure the “Agent Name” matches what you listed in Python

  • Connect your controller to the “AI Controller Class”

../../_images/blueprint-settings.png

  • Check “Simulate Physics” and uncheck “Enable Gravity”

../../_images/blueprint-physics.png

Note

If you have any issues with connecting your agent, please compare against other agent meshes and blueprints found in the Content/HolodeckContent/Agents folder.

Finally, you need to connect your Python class and C++ code to the UE pawn.

  • Navigate to Content/ in the content browser and open up HolodeckGameModeBP

  • Find the entry called “Agent Bp Map” on the right under the Default section. Expand it, and insert a new entry

  • On the left choose whatever you put as agent_type in your code before, and on the right, choose the blueprint (CustomAgentBp) that we just created

../../_images/gamemode-blueprint.png

Repackage your environment (see Developing Environments). You should now be able to use your new agent!

Debugging Tools

To be able to visualize the bounding box and surface points to make sure they’re placed currently, you can use the inherited functions ShowBoundingBox() and ShowSurfacePoints() functions in your agent’s tick method.